Translocations of the MLL (Mixed Lineage Leukemia) gene are frequently found in human leukemias affecting both children and adults. Fusion of MLL to one of more than 60 genes results in generation of oncogenic proteins upregulating Hox genes that are vital to blood cell development. Patients harboring fusion of the MLL gene suffer from aggressive leukemias and poorly respond to available therapies. All of the oncogenic fusion proteins have a preserved N-terminal fragment of MLL that has been identified to interact with menin. It has been recently discovered that association with menin is critical to the leukemogenic activity of the MLL fusion oncoproteins. Selective targeting of the menin-MLL interaction has been emphasized as an effective therapeutic approach for the MLL-related leukemias. We propose to use HTS to develop small molecule inhibitors of the menin-MLL interaction as a potential therapeutic approach for acute leukemias related to MLL-translocations. No attempts to develop small molecule inhibitors of the menin-MLL interaction were reported to date. As a step in this direction, we have developed a fluorescence polarization (FP) assay for efficient screening of the MLPCN compound library at 10 5M concentration to identify inhibitors of this protein-protein interaction. To eliminate "false-positives" and identify ligands targeting menin we have optimized the secondary screenings by application of HTRF and NMR saturation transfer difference (STD) experiments. In this proposal we delineate an efficient strategy to combine HTS based on FP, HTRF and STD assays to develop inhibitors of the menin-MLL interaction, and then optimize their activities by medicinal chemistry approaches. Initial screening of small library of compounds resulted in identification of several weak ligands, demonstrating feasibility of such an approach. The most potent compounds developed and optimized within this proposal will be tested using appropriate leukemia cell- lines harboring MLL translocations. We believe that we will initiate a successful collaborative project to develop chemical compounds that may constitute a novel approach for treatment of acute leukemias related to genetic disorders of MLL gene. Furthermore, this work will facilitate the understanding of biological consequences of inhibiting the menin-MLL interaction and its impact on the disease development. PUBLIC HEALTH RELEVANCE: We propose to use high throughput screening (HTS) to develop chemical compounds that may reverse the oncogenic function of proteins causing acute leukemia. Ultimately, such compounds could be used as highly specific drugs for treatment of patients with aggressive forms of leukemia, which poorly respond to current therapies. [unreadable] [unreadable] [unreadable]